Calibrating crop row computer vision system

ABSTRACT

System and techniques for calibrating a crop row computer vision system are described herein. An image set that includes crop rows and furrows is obtained. Models of the field are searched to find a model that best fits the field. A calibration parameter is extracted from the model and communicated to a receiver.

PRIORITY CLAIM

This application is a continuation of Ser. No. 16/509,188, filed Jun.11, 2019, which claims the benefit of priority to U.S. Application Ser.No. 62/696,741 filed on Jul. 11, 2018, entitled CALIBRATING CROP ROWCOMPUTER VISION SYSTEM, the entire contents of which are herebyincorporated in their entirety.

TECHNICAL FIELD

Embodiments described herein generally relate to computer vision systemsfor vehicles and more specifically to calibrating a computer visionsystem used to navigate lanes or rows, such as crop related rows.

BACKGROUND

Many crops that are farmed are row crops. Row crops are arranged intorows that are generally equally spaced parallel rows in a fieldseparated by furrows. Tending row crops generally involves passingagricultural equipment (AEQ) (e.g., tractors, planters, harvesters,irrigators, fertilizers, etc.) over the field. Generally, the AEQ shouldfollow the rows such that support structures (e.g., wheels, treads,skids, etc.) remain in the furrows so as not to damage the crops.Further, equipment dealing directly with the crops should follow thecenterline of the crop rows.

Navigation systems using an external location mechanism have beenemployed to facilitate automatic navigation of AEQ. These systemsinclude using global position system (GPS) units to locate the positionof AEQ with respect to crop rows. Generally, these systems use aninitialization operation to determine positions through which the AEQshould pass and then provide information about the current position ofAEQ in a field to facilitate navigation. An example initializationoperation can include using a GPS unit to record the movement of AEQ asthe row crops are planted. This recording can later be used to guide theAEQ for subsequent operations.

Computer vision (CV) can be used to guide AEQ down the crop rows. CV canbe superior to external location mechanisms when for example, theexternal location mechanism is compromised (e.g., has inaccurate orabsent positioning) or has not been initialized. A CV navigation systemgenerally involves a sensor, such as a camera, mounted on the AEQ tocollect features of the environment. These features can be used toascertain AEQ position relative to a crop related row (e.g., a crop rowor a furrow) positions and provide that information as parameters to asteering controller to control the AEQ.

Often, CV steering systems ascertain two guidance parameters that areprovided to the steering controller: track-angle error (TKE) andcross-track distance (XTK). TKE involves the angle between the forwarddirection of the AEQ and the rows such that, when the AEQ is followingthe rows the TKE is 0° and when the AEQ is moving parallel to the rowsthe TKE is 90°. Accordingly, the TKE can be considered the currentangle-of-attack for AEQ moving towards a given row. The XTK distance isthe distance between the current position of the AEQ and the croprelated row. Using TKE and XTK as parameters to the steering module canallow for an effective row guidance system of AEQ using CV. Thus, costsand error can be reduced in performing an initialization operation forGPS based systems, or for automatic navigation of AEQ when GPS, or othernavigation systems, are unavailable.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which are not necessarily drawn to scale, like numeralscan describe similar components in different views. Like numerals havingdifferent letter suffixes can represent different instances of similarcomponents. The drawings illustrate generally, by way of example, butnot by way of limitation, various embodiments discussed in the presentdocument.

FIG. 1 is an example of an environment including a system forcalibrating a crop row CV, according to an embodiment.

FIGS. 2A-2B illustrate various components and relationships of an AEQ inan operating environment, according to an embodiment.

FIG. 3 illustrates a block diagram of a system for multiple perspectivecalibration, according to an embodiment.

FIG. 4 illustrates fitting of a model to a segment of an image toimplement a single perspective calibration, according to an embodiment.

FIG. 5 illustrates a convolutional fitting of a model to a segment of animage, according to an embodiment, according to an embodiment.

FIG. 6 illustrates a flow diagram of an example of a method forcalibrating a crop row CV, according to an embodiment.

FIG. 7 is a block diagram illustrating an example of a machine uponwhich one or more embodiments can be implemented.

DETAILED DESCRIPTION

As noted above, crop row navigation entails using image information todetermine TKE and XTK. Generally, the detection of crop related rows,and subsequent determination of TKE and XTK are performed in units ofthe image (e.g., pixels) and not in navigational units such as meters,feet, radians, etc. Because the navigational units are likely the unitsused by the AEQ's steering controller, a conversion from the image unitsto the navigational units is performed. Often, this conversion isaccomplished via a homography. The homography is a function thattranslates points between perspectives of a scene, such as a field. Theposition, angle, and optical characteristics of a camera, for example,define the perspective of the camera. The homography can translate thepoints (e.g., crop row pixels or furrow pixels) to a differentperspective (e.g., straitening the rows in the image). Also, somethingwith a known scale in one perspective—such as five pixels in the bottomscanline of the image equals three feet—can be used to determinedistances at other instances of the image that have a different scale(e.g., the closer to the top of the image, the more feet each pixelrepresents).

Several parameters are used in the homography, including an angle withwhich the camera observes the field (e.g., the pitch), and a height(e.g., distance) of the camera from the field. Other factors can includea yaw or roll of the camera. Generally, these parameters areconfiguration parameters of the CV system, entered at the time ofmanufacture, or a later time (e.g., by a technician in the field). Whileyaw and roll can generally be controlled for using the camera mount onthe AEQ, such as by a leveling mount to control roll, or by aligning thecamera with the AEQ to address yaw, the camera pitch and height can bevariable depending on the AEQ, and even as the AEQ traverses the field.This can be an issue when the CV system is an aftermarket addition forseveral AEQs; each installation involving measuring and adjusting thepitch and height parameters. Entering these parameters can be bothtedious and error prone, possibly resulting in a poor user experience orin a poorly performing CV navigation system.

To address the issues above, an automatic calibration of a crop row CVsystems is described herein. Using an image set, the height and pitch ofa sensor (e.g., camera) to the field can be determined. For example,multiple images-either from two sensors simultaneously, or from onecamera in two or more physical locations—can be compared forcoincidences and disparities. The coincidences can be used to identify acrossing point of the respective perspectives of the different images.Using a known relationship between the perspectives (e.g., two cameraswith a known distance from each other and angle of alignment withrespect to each other), both the pitch and the distance can betrigonometrically ascertained.

Multiple images can involve a more expensive set of equipment (e.g.,more sensors, tighter installation or manufacturing tolerances, etc.).This issue can be addressed by using an image set with a single image.Here, a model (e.g., a numerical or mathematical model) such as afunction, can be matched to, or used to approximate or emulate, the croprelated rows, where a wavelength of the function (e.g., the period of apredictable or repeating part of the function) approximating a distancebetween rows of the same type (e.g., between crop rows). Given a knowntype of crop, different periods of the function can be fit to the imageto determine a scaling of the rows in the image. This scaling can thenbe used to ascertain the calibration parameters. Additional details andexamples are described below.

A model can include a periodic function (e.g., a sine or triangularfunction), quasiperiodic function, almost periodic function, or anyother type of function or mathematical construct, such as a function ormathematical construct that includes one or more periods of apredictable pattern. In an example, a model can be selected based onground coordinates (e.g., physical space coordinates) of crop rows, suchas to cause peaks or troughs of the selected model to match or alignwith the crops and furrows of one or more crop row. Such model can beperiodic in the ground or physical space coordinate plane due to fixedcrop row spacing. Such periodic model can be transformed, such as by ahomographic transformation, to the image or pixel coordinate plate toperform the modeling operations described herein. Such transformationcan cause the transformed model to lose periodicity, such as to causethe model to become quasiperiodic or almost periodic, due to compressionat the edges (e.g., the left and right edges) of an image relative tothe center of the images. In another example, a model can be selectedbased on image or pixel space coordinates, such as to match or alignwith a distribution of crop rows in an image. In particular examples, amodel (e.g., a periodic model or function such as sign function) can beselected to approximate the semi-periodic or near periodic distributionof crop rows in an image.

The terms “period”, “cycle”, or “wavelength”, as used herein, can referto a period, cycle, or wavelength of a periodic, quasiperiodic, almostperiodic model. The terms “period”, “cycle”, or wavelength can alsorefer to a predictable or repetitive portion of any model or functionused for the modeling or convolution techniques described herein.

FIG. 1 is an example of an environment including a system 105 forcalibrating a crop row CV, according to an embodiment. The environmentincludes an AEQ 125, such as a tractor, truck, drone, or other vehiclesituated proximate to crop related rows. The AEQ 125 includes a sensor120, such as a camera, and the system 105. The sensor 120 operates byreceiving light, which can be in the visible spectrum, ultraviolet, orinfrared, or combinations thereof. In an example, the sensor 120 is onlya light sensor, and is not a pattern-based or timing-based depth sensor,for example. Accordingly, the output of the sensor 120 is an image whereelements (e.g., pixels, regions, etc.) represent wavelengths (e.g.,colors) or intensities (e.g., luminance) of light.

The sensor 120 is mounted to the AEQ 125 and provides images of thefield. In an example, the sensor 120 is an array of light sensors, suchas cameras, with known positions and perspective relative to each other.In an example, the sensor 120 is a single light sensor (e.g., camera).In an example, the single light sensor is arranged to change itsposition to provide multiple perspectives at different points in timewhen the AEQ 125 is not moving.

The system 105 includes processing circuitry 110 and a memory 115 (e.g.,computer readable media). The memory 115 is arranged to hold data andinstructions for the processing circuitry 110. As noted above, severalcalibration parameters of the sensor 120 are used in a homography totranslate measurements (e.g., crop related row detection. TKE, XTK,etc.) made in image units (e.g., pixels) into navigational units (e.g.,meters). To implement automatic calibration of one or more of thesecalibration parameters, the processing circuitry 110 is arranged toobtain an image set of a field. Members of the image set include arepresentation of the field, the representation including both crop rowsand furrows. Here, obtaining an image of the image set can include theprocessing circuitry 110 retrieving the image from a buffer (e.g., inthe memory 115) or receiving the image (e.g., directly from the sensor120 via direct memory access (DMA) or the like). (e.g., retrieved orreceived).

In an example, the image set includes multiple images from differentperspectives. In an example, the multiple perspectives are from multiplelight sensors. In an example, the multiple perspectives are from asingle light sensor in two different physical positions (e.g., thesensor 120 captures an image, moves, and then captures another image).In an example, the image set includes images from one perspective. In anexample, the single perspective image is a color image. In an example,the single perspective image is an intensity image derived from a colorimage (e.g., multiple color channels are transformed into a singlechannel for pixels in the image). An intensity image has a single valuerepresentation for any point in the image. Thus, in an example, theintensity image is implemented as a grayscale image. In an example, acrop row is lighter (e.g., has a greater value) than a furrow.Generally, a standard grayscale image uses luminance as the intensitymeasured at any given pixel. However, different manipulations to a colorimage can be performed to, for example, increase the contrast betweendifferent types of crop related rows. Thus, for example, if a crop rowis a first color and a furrow is a second color, then the first colorcan be scaled to be the most intense and the second color scaled to bethe least intense. In an example, the intensity image is binary, withpositions being either one value (e.g., a one) or another value (e.g., azero). Such an image can be easier to process and store, and can beachieved in several ways, including threshold clustering, or other colortransformations.

The processing circuitry 110 is arranged to search models of the fieldto find a model that best fits the field represented in the image set.In an example, where the image set includes multiple images, theprocessing circuitry is arranged to match a common feature of the fieldacross the multiple images. Thus, the multiple images are registered toeach other. Once aligned, differences in other parts of the image canprovide the sensor pitch or height. In an example, this matching is aniterative process that stops when one of a quality metric is reached(e.g., the common feature is within a threshold distance between themultiple images) or a predefined number of iterations have elapsed. Inthis last example, a model that best fit the disparity between themultiple images when the iterations where halted is the selected model.An example of a system employing this iterative process is describedwith respect to FIG. 3.

In an example, where the image set is a single perspective (e.g., asingle image), the models are a periodicity of crop rows or furrows. Inan example, this matching is an iterative processes where differentperiodicities are compared against the crop rows or furrows in thesingle perspective image until a match is found. In an example, themodels are finite. Here, a match is a model that is a better fit thanother models.

In an example, to match the different periodicities, the processingcircuitry 110 is arranged to segment the image to produce a set of imagesegments. In an example, segments in the set of image segments arescanlines (e.g., raster rows) of the image. Other example segments caninclude partial scanlines, multiple scanlines, a sampling of scanlines(e.g., not all scanlines), etc. Generally, each segment will includemultiple crop related rows of one type (e.g., two or more furrows). Inan example, the segments are sized to fit within a buffer (e.g., aregister), such as in the memory 115. Such sizing can, in an example,enable efficient single instruction multiple data (SIMD) processing ofthe image. FIGS. 3A and 3B illustrate an example segmentation.

The processing circuitry 110 is arranged to shift a model acrossrespective segments of the set of image segments to get a set ofpositions. The shifting is an example of a convolution on the imagesegments. The model, such as a sine wave, triangular wave, square wave,etc. is compared against the data in the image segment to fit to thatdata. Here, the set of positions are based on the models, such as thetops or bottoms of a sine wave.

In an example, shifting the model across respective segments includesshifting the model across several segments in parallel. That is, withrespect to calculating the set of positions, the image segments areindependent of each other. Thus, each image segment can yield a set ofpositions without impacting the processing of any other segment. Thisparallelism can benefit many hardware configurations, such as the SIMDcapabilities of GPUS to quickly calculate the positions. The independentnature of these calculations can also be efficiently processed byclusters of processing circuits even if inter-circuit communicationshave high latencies, such as can occur in several FPGAs or ASICscommunicating on a bus, between a co-processor and a processor, or evento other devices connected to the system 105 via a network (e.g., wiredor wireless).

In an example, to shift the model across respective segments, theprocessing circuitry 110 is arranged to use a first period on a firstsegment and a second period on a second segment. In an example, thefirst period and the second period are respectively selected based on arespective position of the first segment and the second segment in theimage. These examples address an issue whereby the perspective of thefield provided by the sensor 120 results in a tapering of crop relatedrows as they move away from the sensor 120. Thus, for the same croptype, portions of the crop related rows will appear closer together atthe top of the image than they will at the bottom of the image. Here, adifferent period (e.g., a shorter period) can be used for segments takenat the top of the image than those at the bottom of the image. In anexample, the first period and the second period are based on a type ofcrop. Thus, once the type of crop is known, a specific set of periodsfor the given model can be used. In an example, the set of periods arearranged in order of the segmentation (e.g., top to bottom). This canspeed retrieval of the periods from the memory 115, for example, via ablock read or the like. In an example, the calibration parameter isderived from a user selection. Here, the user selects or inputs thecrop, a crop row spacing, a center-of crop-to center of furrow distance,etc. at a user interface.

In an example, to shift the model across respective segments of the setof image segments to get the set of positions, the processing circuitry110 is arranged to evaluate the model at a series of positions, startingfrom a first position, until an extremum is found. A positioncorresponding to the extremum is then added to the set of positions. Inan example, the extremum is a maximum. For example, the value of anygiven pixel can be multiplied by the model (e.g., elements of themodel), to achieve a first value. The model can then be shifted by onepixel and multiplied against the pixels of the image segment again. Thisprocess is repeated until a resulting value is smaller than a previousvalue. The previous position is then that which corresponds to themaximum. This shift-multiply-compare technique efficiently operates onseveral architectures, such as GPUs—where the several shifted models ona single segment can be processed in parallel and compared at the end ofa clock cycle—or digital signal processors (DSPs). Also, by locating theposition (e.g., centering a wave top on a crop row) via a maximum valueacross all visible crop rows, for example, the technique is resistant tonoise due to row interruptions (e.g., weeds, missing crops, etc.).

In an example, to shift the model across respective segments of the setof image segments to get the set of positions, the processing circuitry110 is arranged to transform the model and the respective segments ofthe set of image segments to corresponding representations (e.g.,corresponding frequency spectrums) in the frequency domain, such as byusing a Discrete Fourier Transform (DFT). The processing circuitry 110is further configured to multiply frequencies of the frequency domainrepresentation of the model with frequencies of the frequency domainrepresentation of the respective data segments of the set of imagesegments. The result of such multiplication can then be transformed backto the space domain (e.g., by using an inverse DFT), scanned orevaluated to determine an extremum, weighted, and added to a set ofpositions or used to determine the match or fit of the model to the croprelated rows of the respective segments, as described herein.

In an example, the model is a function whose frequency spectrum has asingle frequency, such as a sine function. In such example, to shift themodel across respective segments of the set of image segments to get theset of positions, the processing circuitry 110 is arranged to transformthe respective segments of the set of segments to correspondingfrequency spectrums in the frequency domain, and, for each frequencyspectrum, select a frequency response that corresponds to a frequency ofthe model as the extremum. The location of the extremum can becalculated using an arctangent of a ratio of the imaginary component ofthe frequency response to the real component. Such location can be addedto a set of positions or used to determine the match or fit of the modelto the crop related rows of the respective segments, as describedherein.

In another example, the model is a function whose frequency spectrum hasa single frequency, such as a sine function. In such example, to shiftthe model across respective segments of the set of image segments to getthe set of positions, the processing circuitry 110 is arranged toevaluate the model at a first position, such as by multiplying elementsof the model with corresponding elements of a respective segment andsumming the result to produce a first value. The processing circuitry110 is further arranged to evaluate the model at a second position thatis orthogonal to, or phase shifted 90 degrees from, the first position,to produce a second value. The location of the extremum can becalculated using an arctangent of a ratio of the first value to thesecond value. Such location can be added to a set of positions or usedto determine the match or fit of the model to the crop related rows ofthe respective segments, as described herein.

The techniques described above to match the model are repeated withdifferent periods of the models for a given image segment. The periodthat best fits the crop related rows of a given segment is the matchingmodel. Example details are described with respect to FIGS. 4 and 5.

In an example, the models are a subset of field models. In an example, atype of crop can be received from a user (e.g., via a user interface)and the models can be selected from the field models based on the typeof crop. These examples illustrate that the memory 115 can includeseveral different models for a single crop, and also store severaldifferent sets of these crop-specific models. In an example, thematching can be performed across the different sets of crop-specificmodels. Here, not only can the sensor 120 position calibrationparameters, but the crop can be determined. This crop selectioncalibration parameter can be used in other phases of the AEQ 125navigation or control.

The processing circuitry 110 is arranged to extract a calibrationparameter from the model selected above. In an example, the identifiedmodel is used as an index to a data set of available calibrationparameters. Thus, the processing circuitry 110 uses the identified modelto retrieve the calibration parameter from a database, for example, inthe memory 115. In an example, the model is a data structure thatincludes the available calibration parameters. Here, the processingcircuitry 110 parses the data structure to retrieve the calibrationparameter. In an example, the calibration parameter is a height of thesensor that captured the image set. In an example, the calibrationparameter is a pitch of the sensor that captured the image set. In anexample, the calibration parameter is not a camera yaw of the sensorthat captured the image set. In an example, the calibration parameter isnot a camera roll of a camera that captured the image set.

The processing circuitry 110 is arranged to communicate the calibrationparameter to a receiver. In an example, the calibration parameter isused to transform measurements made on images captured from the sensor120 during navigation into navigational measurements, via a homography,used to control movement of the AEQ 125. Generally, a steeringcontroller of the AEQ 125 is the receiver, however, an intermediary canalso be the receiver where the intermediary uses the homography, andthis the calibration parameter, to calculate the TKE and XTK values forthe steering controller. In an example, the processing circuitry 110 isitself the receiver. In an example, the receiver is a data structure, orlocation, in the memory 115, that can be used by another component ofthe system 105.

FIGS. 2A-2B illustrate various components and relationships of an AEQ inan operating environment, according to an embodiment. FIG. 2A is atop-down view of an AEQ 210 in a field. The shaded portions representcrop rows 215 and the space between the crop rows 215 are furrows 220.The AEQ 210 includes a sensor 205 mounted to the front side of the AEQ210. Here, the AEQ 210 is not aligned with the crop rows 215 or furrows220 but deviates by TKE 225. A steering controller of the AEQ 210 isarranged to steer the AEQ 210 to be in line with the crop rows 215 withwheels in the furrows 220.

FIG. 2B illustrated a side view of the AEQ 210 with the front mountedsensor 205. The height 235 of the sensor 205 and the angle to the ground230 (e.g., pitch of the sensor 205) are calibration parameters for theCV system. It is these parameters that are automatically determined bythe systems and techniques described herein.

FIG. 3 illustrates a block diagram of a system for multiple perspectivecalibration, according to an embodiment. Here, an imaging system 315 isused to capture image data. The image information, combined with knowncharacteristics of the field (e.g., crop spacing data 355) and knowncharacteristics of the sensor (best pitch and height 345), is used tocalculate TKE and XTK 360.

When the system is not calibrated, the normalized image data is providedto a calibration component 320. The calibration component 320 includesan iteration manager 335 that modifies sensor pitch or height parameters340 with each iteration and compares them to the normalized image. Theresult is tested at the quality measurement component 325 using theknown crop characteristics 330. If the result is within a threshold,then the best pitch and height estimation of the sensor is stored 345and can be used by the line extraction component 350. If the result isnot within a threshold, then the iteration manager 335 repeats untilquality measurement 325 is satisfied.

FIG. 4 illustrates fitting of a model to a segment of an image toimplement a single perspective calibration, according to an embodiment.Here, different periods for a model are tested to determine whichmatches the crop rows. The top period is too small, the bottom period istoo large, and thus the middle period 425 is the best fit. The best fitperiod is generally specific to a given crop (e.g., the crop rowplacement or distance from each other) as well as which portion of theinput image is used. At a given scanline of the image, for example, alower scanline will likely have a longer period than a higher (e.g.,closer to the top of the image) scanline due to the sensor'sperspective. The specific period that matches a specific scanline, suchas the bottom scanline, can be used to determine the height of thesensor. In an example, the relationship between periods at differentscanlines can be used to determine the pitch of the sensor.

FIG. 5 illustrates a convolutional fitting of a model to a segment of animage, according to an embodiment. In the illustrated example, thesegment 505 is a scanline (e.g., horizontal row of pixels), where whitepixels represent furrows and shaded pixels represent crop rows. Themodel 510 started in the position represented by the dots and wasiteratively moved 515 to its current position. Here, the maxima 520corresponds to the first center of the crop row pixels and the minimumcorresponds to the first center of furrow pixels. Not that the otherextremum of the model 510 can be used as respective centers for croprows and furrows.

The illustration also highlights possible processing techniques. Forexample, each wavelength of the model can be represented as a pixelwindow, with each pixel in the window being multiplied by a value basedon its position (e.g., the first pixel is multiplied by ten, the secondby eight, the third by two, etc.) to represent the value of the model.The scanline can then be shifted by one pixel (e.g., the first pixel isdiscarded, all other pixels are shifted, and a new pixel is added in thelast position) and the calculation re-run. Thus, the scanline can besegmented by the windows (e.g., offsets of a multiple of the windowsize) and provided as data to a SIMD processor to compute values inparallel. It is also possible to generate one or more models withdifferent shifts, or different periods (e.g., different window sizes),by using different segments of the scanline and providing the segmentsto different execution units in the SIMD processor, effectivelyprocessing several tests in parallel.

FIG. 6 illustrates a flow diagram of an example of a method forcalibrating a crop row CV, according to an embodiment. The operations ofthe method 600 are performed on hardware, such as that described aboveor below (e.g., processing circuitry).

At operation 605, an image set of a field that includes crop rows andfurrows is obtained. In an example, the image set includes multipleimages from different perspectives. In an example, the multipleperspectives are from multiple sensors. In an example, the multipleperspectives are from a single sensor in two different physicalpositions (e.g., the sensor captures an image, moves, and then capturesanother image). In an example, the image set includes images from oneperspective. In an example, the single perspective image is a colorimage. In an example, the single perspective image is an intensity imagederived from a color image (e.g., multiple color channels aretransformed into a single channel for pixels in the image).

At operation 610, models of the field are searched to find a model thatbest fits the field represented in the image set. In an example, wherethe image set includes multiple images, searching the models of thefield include matching a common feature of the field across the multipleimages. In an example, this matching is an iterative process that stopswhen one of a quality metric is reached (e.g., the common feature iswithin a threshold distance between the multiple images) or a predefinednumber of iterations have elapsed.

In an example, where the image set is a single perspective (e.g., asingle image), the models are a periodicity of crop rows or furrows. Inan example, this matching is an iterative processes where differentperiodicities are compared against the crop rows or furrows in thesingle perspective image until a match is found. In an example, themodels are finite. Here, a match is a model that is a better fit thanother models.

In an example, the models are a subset of field models. In an example, atype of crop can be received from a user (e.g., via a user interface)and the models can be selected from the field models based on the typeof crop.

At operation 615, a calibration parameter is extracted from the model.In an example, the calibration parameter is a height of the sensor thatcaptured the image set. In an example, the calibration parameter is apitch of the sensor that captured the image set. In an example, thecalibration parameter is not a camera yaw of the sensor that capturedthe image set. In an example, the calibration parameter is not a cameraroll of a camera that captured the image set.

At operation 620, the calibration parameter is communicated to areceiver. In an example, the calibration parameter is used to transformmeasurements made on images captured from the sensor during navigationinto navigational measurements, via a homography, used to controlmovement of the agricultural equipment.

FIG. 7 illustrates a block diagram of an example machine 700 upon whichany one or more of the techniques (e.g., methodologies) discussed hereincan perform. Examples, as described herein, can include, or can operateby, logic or a number of components, or mechanisms in the machine 700.Circuitry (e.g., processing circuitry) is a collection of circuitsimplemented in tangible entities of the machine 700 that includehardware (e.g., simple circuits, gates, logic, etc.). Circuitrymembership can be flexible over time. Circuitries include members thatcan, alone or in combination, perform specified operations whenoperating. In an example, hardware of the circuitry can be immutablydesigned to carry out a specific operation (e.g., hardwired). In anexample, the hardware of the circuitry can include variably connectedphysical components (e.g., execution units, transistors, simplecircuits, etc.) including a machine readable medium physically modified(e.g., magnetically, electrically, moveable placement of invariantmassed particles, etc.) to encode instructions of the specificoperation. In connecting the physical components, the underlyingelectrical properties of a hardware constituent are changed, forexample, from an insulator to a conductor or vice versa. Theinstructions enable embedded hardware (e.g., the execution units or aloading mechanism) to create members of the circuitry in hardware viathe variable connections to carry out portions of the specific operationwhen in operation. Accordingly, in an example, the machine readablemedium elements are part of the circuitry or are communicatively coupledto the other components of the circuitry when the device is operating.In an example, any of the physical components can be used in more thanone member of more than one circuitry. For example, under operation,execution units can be used in a first circuit of a first circuitry atone point in time and reused by a second circuit in the first circuitry,or by a third circuit in a second circuitry at a different time.Additional examples of these components with respect to the machine 700follow.

In alternative embodiments, the machine 700 can operate as a standalonedevice or can be connected (e.g., networked) to other machines. In anetworked deployment, the machine 700 can operate in the capacity of aserver machine, a client machine, or both in server-client networkenvironments. In an example, the machine 700 can act as a peer machinein peer-to-peer (P2P) (or other distributed) network environment. Themachine 700 can be a personal computer (PC), a tablet PC, a set-top box(STB), a personal digital assistant (PDA), a mobile telephone, a webappliance, a network router, switch or bridge, or any machine capable ofexecuting instructions (sequential or otherwise) that specify actions tobe taken by that machine. Further, while only a single machine isillustrated, the term “machine” shall also be taken to include anycollection of machines that individually or jointly execute a set (ormultiple sets) of instructions to perform any one or more of themethodologies discussed herein, such as cloud computing, software as aservice (SaaS), other computer cluster configurations.

The machine (e.g., computer system) 700 can include a hardware processor702 (e.g., a central processing unit (CPU), a graphics processing unit(GPU), a hardware processor core, or any combination thereof), a mainmemory 704, a static memory (e.g., memory or storage for firmware,microcode, a basic-input-output (BIOS), unified extensible firmwareinterface (UEFI), etc.) 706, and mass storage 708 (e.g., hard drive,tape drive, flash storage, or other block devices) some or all of whichcan communicate with each other via an interlink (e.g., bus) 730. Themachine 70) can further include a display unit 710, an alphanumericinput device 712 (e.g., a keyboard), and a user interface (UI)navigation device 714 (e.g., a mouse). In an example, the display unit710, input device 712 and UI navigation device 714 can be a touch screendisplay. The machine 700 can additionally include a storage device(e.g., drive unit) 708, a signal generation device 718 (e.g., aspeaker), a network interface device 720, and one or more sensors 716,such as a global positioning system (GPS) sensor, compass,accelerometer, or other sensor. The machine 70) can include an outputcontroller 728, such as a serial (e.g., universal serial bus (USB),parallel, or other wired or wireless (e.g., infrared (IR), near fieldcommunication (NFC), etc.) connection to communicate or control one ormore peripheral devices (e.g., a printer, card reader, etc.).

Registers of the processor 702, the main memory 704, the static memory706, or the mass storage 708 can be, or include, a machine readablemedium 722 on which is stored one or more sets of data structures orinstructions 724 (e.g., software) embodying or utilized by any one ormore of the techniques or functions described herein. The instructions724 can also reside, completely or at least partially, within any ofregisters of the processor 702, the main memory 704, the static memory706, or the mass storage 708 during execution thereof by the machine700. In an example, one or any combination of the hardware processor702, the main memory 704, the static memory 706, or the mass storage 708can constitute the machine readable media 722. While the machinereadable medium 722 is illustrated as a single medium, the term “machinereadable medium” can include a single medium or multiple media (e.g., acentralized or distributed database, and/or associated caches andservers) configured to store the one or more instructions 724.

The term “machine readable medium” can include any medium that iscapable of storing, encoding, or carrying instructions for execution bythe machine 700 and that cause the machine 700 to perform any one ormore of the techniques of the present disclosure, or that is capable ofstoring, encoding or carrying data structures used by or associated withsuch instructions. Non-limiting machine readable medium examples caninclude solid-state memories, optical media, magnetic media, and signals(e.g., radio frequency signals, other photon based signals, soundsignals, etc.). In an example, a non-transitory machine readable mediumcomprises a machine readable medium with a plurality of particles havinginvariant (e.g., rest) mass, and thus are compositions of matter.Accordingly, non-transitory machine-readable media are machine readablemedia that do not include transitory propagating signals. Specificexamples of non-transitory machine readable media can include:non-volatile memory, such as semiconductor memory devices (e.g.,Electrically Programmable Read-Only Memory (EPROM), ElectricallyErasable Programmable Read-Only Memory (EEPROM)) and flash memorydevices; magnetic disks, such as internal hard disks and removabledisks; magneto-optical disks; and CD-ROM and DVD-ROM disks.

The instructions 724 can be further transmitted or received over acommunications network 726 using a transmission medium via the networkinterface device 720 utilizing any one of a number of transfer protocols(e.g., frame relay, internet protocol (IP), transmission controlprotocol (TCP), user datagram protocol (UDP), hypertext transferprotocol (HTTP), etc.). Example communication networks can include alocal area network (LAN), a wide area network (WAN), a packet datanetwork (e.g., the Internet), mobile telephone networks (e.g., cellularnetworks). Plain Old Telephone (POTS) networks, and wireless datanetworks (e.g., Institute of Electrical and Electronics Engineers (IEEE)802.11 family of standards known as Wi-Fi®, IEEE 802.16 family ofstandards known as WiMax®), IEEE 802.15.4 family of standards,peer-to-peer (P2P) networks, among others. In an example, the networkinterface device 720 can include one or more physical jacks (e.g.,Ethernet, coaxial, or phone jacks) or one or more antennas to connect tothe communications network 726. In an example, the network interfacedevice 720 can include a plurality of antennas to wirelessly communicateusing at least one of single-input multiple-output (SIMO),multiple-input multiple-output (MIMO), or multiple-input single-output(MISO) techniques. The term “transmission medium” shall be taken toinclude any intangible medium that is capable of storing, encoding orcarrying instructions for execution by the machine 700, and includesdigital or analog communications signals or other intangible medium tofacilitate communication of such software. A transmission medium is amachine readable medium.

ADDITIONAL NOTES & EXAMPLES

Example 1 is a device for calibrating a crop row computer vision system,the device comprising: a memory including instructions; and processingcircuitry that is configured by the instructions to: obtain an image setof a field that includes, crop rows and furrows; search models of thefield to find a model that best fits the field represented in the imageset; extract a calibration parameter from the model; and communicate thecalibration parameter to a receiver.

In Example 2, the subject matter of Example 1 includes, wherein theimage set includes multiple images from different perspectives.

In Example 3, the subject matter of Example 2 includes, wherein, tosearch the models of the field, the processing circuitry is configuredby the instructions to match a common feature of the field across themultiple images.

In Example 4, the subject matter of Example 3 includes, wherein theprocessing circuitry is configured by the instructions to iterativelyperform the matching until one of a quality metric is reached or apredefined number of iterations have elapsed.

In Example 5, the subject matter of Examples 1-4 includes, where theimage set includes images from one perspective.

In Example 6, the subject matter of Example 5 includes, wherein themodels are a periodicity of crop rows or furrows.

In Example 7, the subject matter of Example 6 includes, wherein theprocessing circuitry is configured by the instructions to iterativelycompare different periodicities against the crop rows or furrows until amatch is found.

In Example 8, the subject matter of Example 7 includes, wherein themodels are finite, and wherein a match is a model that is a better fitthan other models.

In Example 9, the subject matter of Examples 1-8 includes, wherein themodels are a subset of field models.

In Example 10, the subject matter of Example 9 includes, wherein theprocessing circuitry is configured by the instructions to: receive, froma user, a type of crop; and select the models from the field modelsbased on the type of crop.

In Example 11, the subject matter of Examples 1-10 includes, wherein thecalibration parameter is a height of a sensor that captured the imageset.

In Example 12, the subject matter of Examples 1-II includes, wherein thecalibration parameter is a pitch of a sensor that captured the imageset.

In Example 13, the subject matter of Examples 1-12 includes, wherein thecalibration parameter is not a yaw of a sensor that captured the imageset.

In Example 14, the subject matter of Examples 1-13 includes, wherein thecalibration parameter is not a roll of a sensor that captured the imageset.

In Example 15, the subject matter of Examples 1-14 includes, wherein thecalibration parameter is used to transform measurements made on imagescaptured from the sensor during navigation into navigationalmeasurements, via a homography, used to control movement of theagricultural equipment.

Example 16 is a method for calibrating a crop row computer visionsystem, the method comprising: obtaining an image set of a field thatincludes, crop rows and furrows; searching models of the field to find amodel that best fits the field represented in the image set; extractinga calibration parameter from the model; and communicating thecalibration parameter to a receiver.

In Example 17, the subject matter of Example 16 includes, wherein theimage set includes multiple images from different perspectives.

In Example 18, the subject matter of Example 17 includes, whereinsearching the models of the field includes matching a common feature ofthe field across the multiple images.

In Example 19, the subject matter of Example 18 includes, wherein thematching is an iterative process that stops when one of a quality metricis reached or a predefined number of iterations have elapsed.

In Example 20, the subject matter of Examples 16-19 includes, where theimage set includes images from one perspective.

In Example 21, the subject matter of Example 20 includes, wherein themodels are a periodicity of crop rows or furrows.

In Example 22, the subject matter of Example 21 includes, wherein thematching is an iterative processes where different periodicities arecompared against the crop rows or furrows until a match is found.

In Example 23, the subject matter of Example 22 includes, wherein themodels are finite, and wherein a match is a model that is a better fitthan other models.

In Example 24, the subject matter of Examples 16-23 includes, whereinthe models are a subset of field models.

In Example 25, the subject matter of Example 24 includes, receiving,from a user, a type of crop; and selecting the models from the fieldmodels based on the type of crop.

In Example 26, the subject matter of Examples 16-25 includes, whereinthe calibration parameter is a height of a sensor that captured theimage set.

In Example 27, the subject matter of Examples 16-26 includes, whereinthe calibration parameter is a pitch of a sensor that captured the imageset.

In Example 28, the subject matter of Examples 16-27 includes, whereinthe calibration parameter is not a yaw of a sensor that captured theimage set.

In Example 29, the subject matter of Examples 16-28 includes, whereinthe calibration parameter is not a roll of a sensor that captured theimage set.

In Example 30, the subject matter of Examples 16-29 includes, whereinthe calibration parameter is used to transform measurements made onimages captured from the sensor during navigation into navigationalmeasurements, via a homography, used to control movement of theagricultural equipment.

Example 31 is a machine readable medium including instructions forcalibrating a crop row computer vision system, the instructions, whenexecuted by processing circuitry, cause the processing circuitry toperform operations comprising: obtaining an image set of a field thatincludes, crop rows and furrows; searching models of the field to find amodel that best fits the field represented in the image set; extractinga calibration parameter from the model; and communicating thecalibration parameter to a receiver.

In Example 32, the subject matter of Example 31 includes, wherein theimage set includes multiple images from different perspectives.

In Example 33, the subject matter of Example 32 includes, whereinsearching the models of the field includes matching a common feature ofthe field across the multiple images.

In Example 34, the subject matter of Example 33 includes, wherein thematching is an iterative process that stops when one of a quality metricis reached or a predefined number of iterations have elapsed.

In Example 35, the subject matter of Examples 31-34 includes, where theimage set includes images from one perspective.

In Example 36, the subject matter of Example 35 includes, wherein themodels are a periodicity of crop rows or furrows.

In Example 37, the subject matter of Example 36 includes, wherein thematching is an iterative processes where different periodicities arecompared against the crop rows or furrows until a match is found.

In Example 38, the subject matter of Example 37 includes, wherein themodels are finite, and wherein a match is a model that is a better fitthan other models.

In Example 39, the subject matter of Examples 31-38 includes, whereinthe models are a subset of field models.

In Example 40, the subject matter of Example 39 includes, wherein theoperations comprise: receiving, from a user, a type of crop; andselecting the models from the field models based on the type of crop.

In Example 41, the subject matter of Examples 31-40 includes, whereinthe calibration parameter is a height of a sensor that captured theimage set.

In Example 42, the subject matter of Examples 31-41 includes, whereinthe calibration parameter is a pitch of a sensor that captured the imageset.

In Example 43, the subject matter of Examples 31-42 includes, whereinthe calibration parameter is not a yaw of a sensor that captured theimage set.

In Example 44, the subject matter of Examples 31-43 includes, whereinthe calibration parameter is not a roll of a sensor that captured theimage set.

In Example 45, the subject matter of Examples 31-44 includes, whereinthe calibration parameter is used to transform measurements made onimages captured from the sensor during navigation into navigationalmeasurements, via a homography, used to control movement of theagricultural equipment.

Example 46 is a system for calibrating crop row computer vision, thesystem comprising: means for obtaining an image set of a field thatincludes, crop rows and furrows; means for searching models of the fieldto find a model that best fits the field represented in the image set;means for extracting a calibration parameter from the model; and meansfor communicating the calibration parameter to a receiver.

In Example 47, the subject matter of Example 46 includes, wherein theimage set includes multiple images from different perspectives.

In Example 48, the subject matter of Example 47 includes, wherein themeans for searching the models of the field include means for matching acommon feature of the field across the multiple images.

In Example 49, the subject matter of Example 48 includes, wherein themeans for matching is iterative and stops when one of a quality metricis reached or a predefined number of iterations have elapsed.

In Example 50, the subject matter of Examples 46-49 includes, where theimage set includes images from one perspective.

In Example 51, the subject matter of Example 50 includes, wherein themodels are a periodicity of crop rows or furrows.

In Example 52, the subject matter of Example 51 includes, wherein themeans for matching is iterative in which different periodicities arecompared against the crop rows or furrows until a match is found.

In Example 53, the subject matter of Example 52 includes, wherein themodels are finite, and wherein a match is a model that is a better fitthan other models.

In Example 54, the subject matter of Examples 46-53 includes, whereinthe models are a subset of field models.

In Example 55, the subject matter of Example 54 includes, means forreceiving, from a user, a type of crop; and means for selecting themodels from the field models based on the type of crop.

In Example 56, the subject matter of Examples 46-55 includes, whereinthe calibration parameter is a height of a sensor that captured theimage set.

In Example 57, the subject matter of Examples 46-56 includes, whereinthe calibration parameter is a pitch of a sensor that captured the imageset.

In Example 58, the subject matter of Examples 46-57 includes, whereinthe calibration parameter is not a yaw of a sensor that captured theimage set.

In Example 59, the subject matter of Examples 46-58 includes, whereinthe calibration parameter is not a roll of a sensor that captured theimage set.

In Example 60, the subject matter of Examples 46-59 includes, whereinthe calibration parameter is used to transform measurements made onimages captured from the sensor during navigation into navigationalmeasurements, via a homography, used to control movement of theagricultural equipment.

Example 61 is at least one machine-readable medium includinginstructions that, when executed by processing circuitry, cause theprocessing circuitry to perform operations to implement of any ofExamples 1-60.

Example 62 is an apparatus comprising means to implement of any ofExamples 1-60.

Example 63 is a system to implement of any of Examples 1-60.

Example 64 is a method to implement of any of Examples 1-60.

The above detailed description includes references to the accompanyingdrawings, which form a part of the detailed description. The drawingsshow, by way of illustration, specific embodiments that can bepracticed. These embodiments are also referred to herein as “examples.”Such examples can include elements in addition to those shown ordescribed. However, the present inventors also contemplate examples inwhich only those elements shown or described are provided. Moreover, thepresent inventors also contemplate examples using any combination orpermutation of those elements shown or described (or one or more aspectsthereof), either with respect to a particular example (or one or moreaspects thereof), or with respect to other examples (or one or moreaspects thereof) shown or described herein.

All publications, patents, and patent documents referred to in thisdocument are incorporated by reference herein in their entirety, asthough individually incorporated by reference. In the event ofinconsistent usages between this document and those documents soincorporated by reference, the usage in the incorporated reference(s)should be considered supplementary to that of this document; forirreconcilable inconsistencies, the usage in this document controls.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one, independent of any otherinstances or usages of “at least one” or “one or more.” In thisdocument, the term “or” is used to refer to a nonexclusive or, such that“A or B” includes “A but not B,” “B but not A,” and “A and B,” unlessotherwise indicated. In the appended claims, the terms “including” and“in which” are used as the plain-English equivalents of the respectiveterms “comprising” and “wherein.” Also, in the following claims, theterms “including” and “comprising” are open-ended, that is, a system,device, article, or process that includes elements in addition to thoselisted after such a term in a claim are still deemed to fall within thescope of that claim. Moreover, in the following claims, the terms“first.” “second,” and “third.” etc. are used merely as labels, and arenot intended to impose numerical requirements on their objects.

The above description is intended to be illustrative, and notrestrictive. For example, the above-described examples (or one or moreaspects thereof) can be used in combination with each other. Otherembodiments can be used, such as by one of ordinary skill in the artupon reviewing the above description. The Abstract is to allow thereader to quickly ascertain the nature of the technical disclosure andis submitted with the understanding that it will not be used tointerpret or limit the scope or meaning of the claims. Also, in theabove Detailed Description, various features can be grouped together tostreamline the disclosure. This should not be interpreted as intendingthat an unclaimed disclosed feature is essential to any claim. Rather,inventive subject matter can lie in less than all features of aparticular disclosed embodiment. Thus, the following claims are herebyincorporated into the Detailed Description, with each claim standing onits own as a separate embodiment. The scope of the embodiments should bedetermined with reference to the appended claims, along with the fullscope of equivalents to which such claims are entitled.

1. (canceled)
 2. A device for calibrating a crop row computer visionsystem, the device comprising: a memory including instructions; andprocessing circuitry that is configured by the instructions to: obtain aset of one or more images of a field that includes crop rows andfurrows, the set of one or more images captured by a sensor associatedwith the computer vision system; iteratively test a set of models on animage from the set of one or more images to select a model of the field,the test based on a correspondence between a periodic component of themodel and the crop rows or the furrows in the image, an iterationincluding: a selection of a period for a function as a current model; atest of the current model for correspondence between a feature of thefunction and the crop rows or the furrows in the image to produce avalue; and a determination of whether the value is better than aprevious value from a previous iteration, iterations terminating inresponse to a predefined iteration limit being reached or to the valuebeing worse than the previous value indicating a maximum extremum isreached, the model corresponding to the maximum extremum, the periodselected at a next iteration to move towards the maximum extremum basedon the determination of whether the value is better than the previousvalue from the previous iteration; determine a scaling of crop rows orfurrows in the image using the model; determine a calibration parameterthat is indicative of a configuration of the sensor relative to thefield based on the scaling of crops rows or furrows; and communicate thecalibration parameter to a receiver.
 3. The device of claim 2, wherein aconvolution of the model is applied across the image to test the model.4. The device of claim 3, wherein the convolution is horizontal.
 5. Thedevice of claim 3, wherein the convolution is vertical.
 6. The device ofclaim 5, wherein the image is divided into horizontal segments withdifferent vertical positions in the image, and wherein the model istested on multiple of the horizontal segments to produce theconvolution.
 7. The device of claim 6, wherein the processing circuitryis configured to perform the test of the model on the multiplehorizontal segments in parallel.
 8. The device of claim 6, wherein thecalibration parameter is a pitch of a sensor that captured the set ofone or more images, and wherein the pitch is determined by differentperiods selected as maximum extremum in different horizontal segments.9. The device of claim 6, wherein a horizontal segment is a scanline ofthe image.
 10. The device of claim 2, wherein the function is a wave.11. The device of claim 10, wherein the feature of the function is a topof the wave or a bottom of the wave.
 12. The device of claim 2, whereinthe calibration parameter is a height of a sensor that captured the setof one or more images.
 13. The device of claim 2, wherein thecalibration parameter is used to transform measurements made on imagescaptured from the sensor during navigation into navigationalmeasurements, via a homography, used to control movement of agriculturalequipment.
 14. A method for calibrating a crop row computer visionsystem, the method comprising: obtaining a set of one or more images ofa field that includes crop rows and furrows, the set of one or moreimages captured by a sensor associated with the computer vision system;iteratively testing a set of models on an image from the set of one ormore images to select a model of the field, the testing based on acorrespondence between a periodic component of the model and the croprows or the furrows in the image, an iteration including: selecting aperiod for a function as a current model; testing the current model forcorrespondence between a feature of the function and the crop rows orthe furrows in the image to produce a value; and determining whether thevalue is better than a previous value from a previous iteration,iterations terminating in response to a predefined iteration limit beingreached or to the value being worse than the previous value indicating amaximum extremum is reached, the model corresponding to the maximumextremum, the period selected at a next iteration to move towards themaximum extremum based on the determination of whether the value isbetter than the previous value from the previous iteration: determininga scaling of crop rows or furrows in the image using the model;determining a calibration parameter that is indicative of aconfiguration of the sensor relative to the field based on the scalingof crops rows or furrows; and communicating the calibration parameter toa receiver.
 15. The method of claim 14, wherein a convolution of themodel is applied across the image during testing.
 16. The method ofclaim 15, wherein the convolution is vertical.
 17. The method of claim16, wherein the image is divided into horizontal segments with differentvertical positions in the image, and wherein the model is tested onmultiple of the horizontal segments to produce the convolution.
 18. Themethod of claim 17, wherein the calibration parameter is a pitch of asensor that captured the set of one or more images, and wherein thepitch is determined by different periods selected as maximum extremum indifferent horizontal segments.
 19. The method of claim 14, wherein thefunction is a wave, and wherein the feature of the function is a top ofthe wave or a bottom of the wave.
 20. The method of claim 14, whereinthe calibration parameter is a height of a sensor that captured the setof one or more images.
 21. The method of claim 14, wherein thecalibration parameter is used to transform measurements made on imagescaptured from the sensor during navigation into navigationalmeasurements, via a homography, used to control movement of agriculturalequipment.